1. Field of the Invention
This invention relates to electrostatic copying or printing devices and more particularly to a fixing station for fixing toner images in such devices.
2. Prior Art
This invention is directed to that class of device utilized for fixing powder toner images applied to a recording carrier such as a paper web by means of solvent vapor. In such devices a guidance mechanism guides the recording carrier through a housing in which the solvent vapor acts on the toner image applied to the paper to fuse the toner image to the paper.
Nonmechanical printing and copying apparatus utilizing electrostatic principles are known to the art. See, for example, U.S. Pat. No. 3,861,863, the teachings of which are herein incorporated by reference. In such devices toner images of the characters to be printed are first applied to a recording carrier such as a paper web. Application of the toner images can, for example, be applied to the paper web electrophotographically or electrographically creating a charged image on a photoelectric or dielectric intermediate carrier, usually a cylinder. The charge images are thereafter developed at a development station by application of a powdered toner. The resultant toner images are then transferred at a transfer station to the paper web. In order to affix the toner images in a smear free fashion to the paper, the toner must subsequently be bonded to the recording carrier at a fixing station.
Fixing stations at which the toner image is fused to the recording carrier are well-known. In one type of known fixing station the recording carrier, after leaving the toner transfer station, passes between two fixing cylinders with at least one of the cylinders heated. Through heat and pressure the toner particles are fused onto the recording carrier or paper. Fixing stations constructed according to this principle have a singular disadvantage in that the writing quality on the paper is or may be unfavorably influenced in numerous ways during passage through the fixing station. For example, the heated toner can adhere to the fixing cylinders and therefore, as a consequence, portions of the image can be mutilated. Additional disadvantages reside in the fact that the energy input for the heating station is relatively high and a rather expensive mechanism is required.
Another known method of fusing the toner to the paper utilizes a solvent vapor. See, for example, U.S. Pat. No. 3,049,810, the teachings of which are herein incorporated by reference. In this type of fixing station, solvent vapor is produced which is of a type capable of melting or liquifying the toner on the paper such that the liquified toner will penetrate the paper. The solvent vapor is supplied by a suitable apparatus directly to the paper in such a manner as to affect the toner images thereon. The fixing station may consist of a recepticle from which the solvent vapor is supplied or in which a vaporization device for the solvent is positioned. The fixing station generally includes a paper guiding mechanism by means of which the recording carrier or paper is guided through the recepticle. Preferably the fixing station is designed such that solvent vapors will not escape from it.